The use of graphical dynamic system simulation software is becoming more popular as automotive engineers strive to reduce the time to develop new control systems. The use of model-based control methods designed to meet future emission and diagnostic regulations has also increased the need for validated engine models. A previously validated, nonlinear, mean-torque predictive engine model* is converted to MATLAB / SIMULINK† to illustrate the benefits of a graphical simulation environment. The model simulates a port-fuel-injected, spark-ignition engine and includes air, fuel and EGR dynamics in the intake manifold as well as the process delays inherent in a four-stroke cycle engine. The engine model can he used in five ways: As a nonreal-time engine model for testing engine control algorithms As a real-time engine model for hardware-in-the-loop testing As an embedded model within a control algorithm or observer As a system model for evaluating engine sensor and actuator models As a subsystem in a powertrain or vehicle dynamics model Although developed and validated for a specific engine, the model is generic enough to be used for a wide range of spark-ignition engines. Modular programming techniques reduce model complexity by dividing the engine and control system into hierarchical subsystems.